Chapter 34 - Animals

1. Chapter 34 - Animals 34.2 Animal Bodies

2. Morphology is • the branch of biology dealing with the form and structure of organisms. • Symmetry is • the proper proportion of the parts of a body with respect to one another and with regard to size and form. Body Structure

3. Radial Symmetry • Basic body plan where the organism can be divided into similar halves by passing a plane at any angle along a central axis. • Characteristic of sessile and bottom-dwelling animals, as the sea anemone and starfish. Patterns of Symmetry

4. Bilateral Symmetry • Basic body plan where the left and right sides of the organism can be divided into approximate mirror images of each other along the midline. • Dorsal - back • Ventral - tummy • Anterior - head • Posterior – rear end Bilateral Symmetry – most animals…

5. Cephalization • specialization of the body with sensory and neural organs in an anterior head Bilateral Symmetry…

6. Germ Layers – layers formed during very early development of most animals • 1. ectoderm = outside layer • 2. endoderm = inside layer • 3. mesoderm = layer in between the above two Patterns of Symmetry

7. Most animals have some type of body cavity. • Body Cavity • Fluid-filled space between the digestive tract and the outer wall of the body during development. Examples: • FLATWORM: three germ layers; solid body – lack a body cavity. • ROUNDWORM: Body cavity aids in movement by providing a firm structure against which muscles can contract. Body Cavities…

8. A body cavity also allows some movement of the exterior part of the body in respect to the internal parts of the body. • more freedom of movement for the animal • The fluid in the cavity acts as a reservoir and medium for the transport for nutrients and wastes. • these diffuse in/out of the animal’s body cells. Body Cavities…

9. ANIMAL DIVERSITY • Animal phyla shown on the same branch of the phylogenetic tree are thought to be more closely related to each other than they are to other animals. • They are characterized by important similarities in morphology. • Likewise, animals shown in different parts of the tree are thought to be more distantly related. Animal Diversity…

10. Multicellularity and a limited degree of cell specialization – characterize sponges • Sponges have no organized body shape and no true tissues. • True tissues in two layers – found in the cnidarians (hydra, jellyfish, etc.) and the ctenophores (exclusively marine, invertebrates) • True tissues in three layers and bilateral symmetry – characterize all of the other animal phyla • phylogenetic categories are based on • the absence or presence and type of body cavity • fundamental patterns of development Animal Diversity…

11. Invertebrates • Absence of a backbone • Greatest number of animal species • Most of the animals alive today Animal Diversity…

12. Chordates • Refers to the notochord • A firm, flexible rod of tissue located in the dorsal part of the body (the back). • At some stage of development, all chordates have a notochord, dorsal nerve cord, pharyngeal pouches, and a post anal tail. • Dorsal nerve cord • Hollow tube lying just above (dorsal to) the notochord. • Pharyngeal pouches • Small outpockets of the anterior part of the digestive tract. • Postanal tail • Consists of muscle tissue and lies behind the posterior opening of the digestive tract. Animal Diversity…

13. In most vertebrates… • The dorsal nerve cord develops into the brain and the spinal cord. • This runs within the hollow backbone in aquatic vertebrates (fishes and amphibians). • Pharyngeal pouches evolved into gills – used for breathing. • In most vertebrates, the notochord is seen only in the embryonic stage. • It is replaced by the backbone early in development. Animal Diversity…

14. Vertebrates… • Make up only one subphylum of the phylogenetic tree of all animals. • Humans are vertebrates. • Humans interact extensively with many other vertebrates. • fishes • birds • mammals • All of these are primary food sources for humans. Animal Diversity…